What is LiDAR
Light detection and ranging (LiDAR) technology consists of a transmitter sending laser pulses, a receiver detecting the reflected beams, and a GPS unit to track its location. Similar to radar, a LiDAR system measures the time it takes for an emitted laser pulse to travel to the ground and reflect back to the receiver, with this time being used to calculate the distance the beam has travelled. The distance travelled is then converted to an elevation by utilizing the GPS unit data, which provides the location of the LiDAR source, as well as an Inertial Measurement Unit (IMU) that provides a correction for the orientation of the unit containing the LiDAR system, such as the roll, pitch, and yaw of a plane, helicopter, or drone.
How data is collected
The most widely used LiDAR systems collect ground surveys from the air, being especially suited for cases where large areas of survey data are required or in remote areas where surface surveying from the ground is not practical. Aircraft, both crewed and uncrewed, can be equipped with airborne LiDAR sensors and are combined with GPS and digital cameras to capture photographs and digital scans of the areas.
LiDAR scans can also be performed from ground-mounted equipment on tripods. Each tripod location is noted as a GPS point, and the scan collects data in all directions from that known point. Once a scan has been taken from each point, each scan is linked to create a single data set.
How its used
These LiDAR scans collect a 3-dimensional set of points called ‘point clouds’, which are geographically referenced to GPS coordinates and can be processed to create a digital elevation model (DEM) of the earth’s surface. The DEM models are used to create a topographic surface for transportation planning and design of roads, city planning and infrastructure design, as well as informing projects of ‘as-built’ information to manage at the site once construction is complete. During the design phases of a project, the LiDAR point clouds, along with the design models, are input into a building information model (BIM), which provides a 3D representation of the design for visual reviews and discussion.
LiDAR point clouds collected from ground-based scans are also useful in civil engineering and building design. In retrofits of existing structures, a ground-based scan can be performed to create a 3-dimensional set of data which captures the existing routing of pipes, structures and other previously constructed items. These point cloud models allow engineers to understand where potential clashes may occur when upgrading or renovating an existing building.
Looking forward
As virtual reality (VR) and augmented reality (AR) technology improves, LiDAR data scans, along with the civil design structures, will be able to be incorporated into the VR/AR experience seamlessly. This will allow a project team and involved parties to feel like they are physically walking through a project area from the comfort of their chairs.
Article first published in Applied Technology Review Canada, March 2024. Reprinted with permission.